To meet the demand for wireless data traffic having increased since deployment of 4G communication systems, efforts have been made to develop an improved 5G or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post LTE System’. The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems. In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), reception-end interference cancellation and the like. In the 5G system, Hybrid FSK and QAM Modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.
The Internet, which is a human centered connectivity network where humans generate and consume information, is now evolving to the Internet of Things (IoT) where distributed entities, such as things, exchange and process information without human intervention. The Internet of Everything (IoE), which is a combination of the IoT technology and the Big Data processing technology through connection with a cloud server, has emerged. As technology elements, such as “sensing technology”, “wired/wireless communication and network infrastructure”, “service interface technology”, and “Security technology” have been demanded for IoT implementation, a sensor network, a Machine-to-Machine (M2M) communication, Machine Type Communication (MTC), and so forth have been recently researched. Such an IoT environment may provide intelligent Internet technology services that create a new value to human life by collecting and analyzing data generated among connected things. IoT may be applied to a variety of fields including smart home, smart building, smart city, smart car or connected cars, smart grid, health care, smart appliances and advanced medical services through convergence and combination between existing Information Technology (IT) and various industrial applications.
In line with this, various attempts have been made to apply 5G communication systems to IoT networks. For example, technologies such as a sensor network, Machine Type Communication (MTC), and Machine-to-Machine (M2M) communication may be implemented by beamforming, MIMO, and array antennas. Application of a cloud Radio Access Network (RAN) as the above-described Big Data processing technology may also be considered to be as an example of convergence between the 5G technology and the IoT technology.
A Long Term Evolution (LTE) system of a standard organization of 3rd Generation Partnership Project (3GPP) supports three types of frame structures, which includes Frequency Division Duplex (FDD) and Time Division Duplex (TDD). FDD and TDD are deployed on a licensed band generally. Further, a third frame structure is used on an unlicensed band, which coexists with other wireless access technologies based on the technology of ‘listen before talk’ (LBT) transmission, that is detection before transmission. For the three types of frame structures, a wireless frame with a length of 10 ms is configured and it is equally divided into 10 sub-frames with a length of 1 ms. Wherein, a sub-frame consists of two consecutive time slots each with a length of 0.5 ms. That is, the kth sub-frame includes time slot 2 k and time slot 2 k+1, wherein k equals to 0, 1, . . . 9. FIG. 1 shows a frame structure of a TDD system. Each wireless frame is divided into two half-frames with a length of 5 ms. Each half-frame includes 8 time slots each with a length of 0.5 ms and 3 special fields, i.e., a downlink pilot time slot (DwPTS), a guard period (GP) and an uplink pilot time slot (UpPTS). And the total length of these special fields is 1 ms. For the third frame structure, a partial sub-frame structure is also supported, that is, a start part of the sub-frame is used for downlink transmission, which is equivalent to DwPTS. One downlink transmission time interval (TTI) is defined on one sub-frame.
In the LTE system, a wider working bandwidth may be obtained by adopting carrier aggregation (CA) technology, wherein one cell is Primary Cell (Pcell), and other cells are secondary Cells (Scells). The third frame structure deployed on the unlicensed band may be configured to be Scell, that is, the cell in another licensed band is configured to be Pcell.
In the LTE system, for the uplink data transmission, an uplink grant signaling (UL-Grant) sent in downlink sub-frame n is to schedule data transmission in uplink sub-frame n+k. In an FDD system, k may equal to 4. In a TDD system, due to limitations of the frame structure, k may be larger than or equal to 4. For the third frame structure, according to the discussion progress of the current standardized conference, a timing relationship between the UL-Grant and uplink data scheduled by the UL-Grant may be dynamic, but its time delay still needs to be larger than or equal to 4.
According to the existing LTE specifications, when there is no Physical Uplink Control Channel (PUCCH) transmission, a transmission power of the physical uplink shared channel (PUSCH) in sub-frame i of a cell c may be determined according to the following formula:
            P              PUSCH        ,        c              ⁡          (      i      )        =      min    ⁢          {                                                                                    P                                      CMAX                    ,                    c                                                  ⁡                                  (                  i                  )                                            ,                                                                                          10                ⁢                                                                  ⁢                                                      log                    10                                    ⁡                                      (                                                                  M                                                  PUSCH                          ,                          c                                                                    ⁡                                              (                        i                        )                                                              )                                                              +                                                P                                      O_PUSCH                    ,                    c                                                  ⁡                                  (                  j                  )                                            +                                                                    α                    c                                    ⁡                                      (                    j                    )                                                  ·                                  PL                  c                                            +                                                Δ                                      TF                    ,                    c                                                  ⁡                                  (                  i                  )                                            +                                                f                  c                                ⁡                                  (                  i                  )                                                                        }        ⁢                                   [          dBm          ]                ,            wherein, each parameter in the above formula is defined in section 5.1.1.1 of 36.212 of the 3GPP specification in detail. And these parameters are briefly introduced as follows: PCMAX,c(i) refers to a maximum transmission power of a UE configured in cell c; MPUSCH,c(i) refers to the number of PRBs occupied by the PUSCH; PO_PUSCH,c(j) refers to a power offset configured by a higher layer signaling; PLc refers to a link loss; αc(j) refers to all or part of a control compensation link loss; fc(i) refers to an accumulated value controlled by closed loop power; and ΔTF,c(i) refers to a parameter related to MCS of an uplink transmission. Specifically speaking, when parameter Ks equals to 1.25, ΔTF,c(i)=10 log10((2BPRE·Ks−1)·βoffsetPUSCH). For a case in which only A-CSI is sent and uplink data are not sent, BPRE=OCQI/NRE,βoffsetPUSCH=βoffsetCQI. For a case in which the uplink data are sent,
      BPRE    =                  ∑                  r          =          0                          C          -          1                    ⁢                        K          r                /                  N          RE                      ,            β      offset      PUSCH        =    1.  C refers to the number of CBs divided by one TB; Ks refers to the number of bits of the rth CB and NRE refers to the total number of REs included in the PUSCH channel.
According to the discussion progress of the current standardized conference, on a carrier of the unlicensed band, the allocation granularity of the uplink PUSCH channel of the UE is one interlace. For example, as shown in FIG. 2, one interlace includes 10 PRBs, and they are distributed on the whole bandwidth at equal intervals, that is, the interval is 10 PRBs. When such PUSCH resource allocation structure is adopted, in one aspect, uplink energy of LAA is distributed on the whole system bandwidth; in the other aspect, under a premise of meeting a certain Power Spectral Density (PSD), the transmission power of the UE in one PRB may be improved, thus in a case that only one interlace is allocated by the UE, uplink transmission may still be performed with a higher power. Herein, in a case of increasing the transmission power of the UE, the problem to be solved is how to ensure friendly coexistence with other devices.
In fact, power adjustments of devices need a transition time. For example, when a device without data transmission strats a data transmission, the transmission power of the device would increase from a very low value or 0, such as an OFF power, to a transmission power, which would not be stable in a set power, such as an ON power, till a certain transition time has lapsed. The certain transition time may be named as a power increase transition time hereinafter. Accordingly, when the transmission power of the device decreases from a higher value, such as an ON power to a transmission power, which would not be stable in a very small power value or power value 0, such as an OFF value, till a certain transition time has lapsed. The certain transition time would be named as power decrease transition time hereinafter. According to the existing LTE specifications, as shown in FIG. 3, for uplink data transmission, the power increase transition time of the UE may be 20 us after the start time of uplink transmission scheduled by a base station; and the power decrease transition time of the UE may be 20 us after the end time of uplink transmission scheduled by the base station. According to the existing LTE specifications, as shown in FIGS. 4 and 5, for a PRACH and an SRS, the power increase transition time of the UE may be 20 us before start time of the PRACH and the SRS; and the power decrease transition time of the UE may be 20 us after end time of the PRACH and the SRS. According to 3GPP RAN4 specifications, there are no demands on an instantaneous value of the transmission power of the device in the transition time. However, the transmission power of the device is required to reach a required value after the transition time.
According to the discussion progress of the current standardized conference, multiple LBT solutions for uplink transmission may exist. One solution is LBT type 4 (CAT-4). That is, the device may generate a random number N according the size of a certain contention window (CW). Then the channel may only be occupied when the number of idle channels reaches N. Herein, the device may instantly send a filling signal occupying the channel till a start timing of the uplink transmission scheduled, and then starts the uplink transmission scheduled. Or, the device may execute a Self-Defer process, and start the scheduled uplink transmission only when the channel is detected to be idle for a length of time T0 before the start timing of the uplink transmission scheduled. For example, T0 may equal to 25 us, Another solution is LBT type 2 (CAT-2). That is, the device may occupy the channel as long as the device detects that the channel is idle for a length of time T1 before the start timing of the uplink transmission scheduled. For example, T1 may equal to 25 us. The basic principle of the LBT mechanisms is to avoid collision from other devices by detecting whether a CCA time slot is idle. In addition, the LBT solution may be NO LBT. That is, the device may start an uplink transmission directly without executing LBT after deferring a time period no longer than T3 from the end of a downlink transmission. For example, T3 may equal to 16 us, which is consistent with the short inter-frame space (SIFS) of WiFi. NO LBT may be considered that the LBT must be successful after the time of T3.